Do you mean the place with the excavation sites (with Unown)? If so, all you have to do is complete the game. That's it!
It is in Four island
You have to win the champion
In icefall cave.
The only dark type Pokemon you can get in firered is murkrow which happens to be in lost cave on five island.
icefall cave on island 4
Four Island, Icefall Cave.
It is in Island four.
It's in the Icefall Cave on Four Island.
its located on four island in the cave
In Icefall Cave, in Four Island
In Icefall Cave, in Four Island
In icefall cave at four island.